Doing postal surveys

Information on research, statistics and publications - tips including how to recruit participants, gain funding, understand your results and get them published.
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Paul Wicks
Posts: 26
Joined: Sun Mar 25, 2007 6:43 pm

Doing postal surveys

Post by Paul Wicks » Fri Mar 30, 2007 9:27 am


- Using an identification number rather than personal details
- Design: required to write identifier only once; demographic details at the end; care with initial items (easier first); initial items addressed respondents' concerns
- Postcard reminders
- Shorter questionnaires
- Distributed by hand
- Cover letter
- (Significant enough) monetary incentive
- Stamped return envelope
- Green paper(!)
- Pre-notification letter

The best review is this one: Edwards et al 2002, Increasing response rates to postal questionnaires: systematic review, BMJ 2002;324:1183

Response rates:

Response rates from people with whom you have had no previous contact can be expected to be about 15-25%. Response rates from various patient groups are around 30-60%.

Response rates to advertising (maildrops, leaflets) are generally 1-2%, but can be executed in bulk, particularly by a commercial company either with newspapers (cheaper) or by themselves (a "solus" drop). There is also the advantage that most firms can target by postcode.

Response rates are lower in surveys addressing sensitive issues.

Here are some tips to maximise response rates in order to hopefully minimise bias:

Send out using first class post, and mark it on the envelope if using a franking machine.

Getting a stamp that says "private and confidential" will make it clear that the envelope is not junk mail.

The use of incentives (money, lollipop, pens) does increase response rates and may reduce bias. Financially, only a small amount is needed (~£5); more than this is not exponentially better.

Longer questionnaires have lower response rates. Questionnaires that have a stem-and-leaf format (i.e. if you answered yes to question 5, please answer questions 6,7,and 8....) are more likely to have missing data that questionnaires with entirely "self contained" items.

Enclose an SSAE, with a first class stamp or freepost business reply service. A study found response rate 6% higher using stamps. (Streiff 2001, A mail survey of United States hematologists and oncologists: A comparison of business reply versus stamped return envelopes. Journal of Clinical Epidemiology, Volume 54, Issue 4, Pages 430-432)

Paper quality has no effect on return rates. However, printing in a different colour may do

Sign using pen, preferably in non-black ink to make it more obvious you have signed it

When sending to patients, using the letterhead of a trusted institution can be helpful, as can mentioning that the work is in collaboration with their doctor.

Check with your ethics committee whether you are allowed to telephone a.) non-responders, b.) people with missing data

Get a pack of blank postcards, print a little label reminding people about your questionnaire or asking them to contact you if you haven't received it, send it out 2 weeks after the initial mailing.

Using email can be good when you need answers quickly and cheaply. You may also be more likely to get more comments to open-ended questions. Obviously the internet-using population are systematically biased so email is only suitable for some uses (e.g. university undergrads, professionals).

To maximise response rates to GPs, it has been suggested that you should send at least three reminders to maximise your response rate (Barclay et al 2002, Not another questionnaire! Maximizing the response rate, predicting non-response and assessing non-response bias in postal questionnaire studies of GPs, Family Practice Vol. 19, No. 1, 105-111).

Other helpful tips:

Get some printable labels to stop you having to write out your return address 300 times

Make sure you weigh everything down the post office. The pack I sent out to people was more than a 1st class stamp would pay for, but they were supposed to keep 90% of it and just send back one sheet so the SSAE just had a first class stamp. Sometimes people would send back the whole thing though, the stamp wasn't enough, and it'd get diverted to the post office with a £1 fine on it. VERY annoying. Also remember the new postal rates charge for size as well as weight.

A LOT of stuff goes missing in the post. Check with your ethics guys if you're allowed to phone to check if people have received it. I'd say about 10% goes missing on the way to them, and about 5% goes missing on its way back from them to you.

For more info:

For a fuller set of literature click here.

Viljoen, D. & Wolpert, M. (2002). Increasing return rates from postal outcome questionnaires: 10 pointers from the literature. Clinical Psychology, 19, 18-21

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Re: Doing postal surveys

Post by Randomswirls » Sun Jun 19, 2016 1:42 pm

The following links are broken:

- you may get more comments to open ended questions
- for a fuller set of literature click here

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